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Articles 1 - 30 of 53
Full-Text Articles in Engineering
Optical Frequency Comb Generation Based On Chirping Of Mach-Zehnder Modulators
Optical Frequency Comb Generation Based On Chirping Of Mach-Zehnder Modulators
Faculty of Engineering University of Malaya
A new approach for the generation of an optical frequency comb, based on chirping of modulators, is proposed and numerically demonstrated. The setup includes two cascaded Mach-Zehnder Modulators (MZMs), a sinusoidal wave oscillator, and an electrical time delay. The first MZM is driven directly by a sinusoidal wave, while the second MZM is driven by a delayed replica of the sinusoidal wave. A mathematical model of the proposed system is formulated and modeled using the Matlab software. It is shown that the number of the frequency lines is directly proportional to the chirp factor. In order to achieve the highest …
Biosensing Enhancement Of Dengue Virus Using Microballoon Mixers On Centrifugal Microfluidic Platforms
Faculty of Engineering University of Malaya
Dengue is the current leading cause of death among children in several Latin American and Asian countries. Due to poverty in areas where the disease is prevalent and the high cost of conventional diagnostic systems, low cost devices are needed to reduce the burden caused by dengue infection. Centrifugal microfluidic platforms are an alternative solution to reduce costs and increase the availability of a rapid diagnostic system. The rate of chemical reactions in such devices often depends on the efficiency of the mixing techniques employed in their microfluidic networks. This paper introduces a micromixer that operates by the expansion and …
Single Phase Transformerless Inverter Topologies For Grid-Tied Photovoltaic System: A Review
Single Phase Transformerless Inverter Topologies For Grid-Tied Photovoltaic System: A Review
Faculty of Engineering University of Malaya
Grid-tied inverters are the key components of distributed generation system because of their function as an effective interface between renewable energy sources and utility. Recently, there has been an increasing interest in the use of transformerless inverter for low-voltage single-phase grid-tied photovoltaic (PV) system due to higher efficiency, lower cost, smaller size and weight when compared to the ones with transformer. However, the leakage current issues of transformerless inverter, which depends on the topology structure and modulation scheme, have to be addressed very carefully. This review focuses on the transformerless topologies, which are classified into three basic groups based on …
An Islanding Detection Strategy For Distribution Network Connected With Hybrid Dg Resources
An Islanding Detection Strategy For Distribution Network Connected With Hybrid Dg Resources
Faculty of Engineering University of Malaya
The exponential growth in electricity demand has driven the Distributed Generation (DG) technology a boost in the power system. The use of DG is beneficial to power utilities, DG owners', and end-users in terms of reliability, power quality, and economics. However, to fully utilize the benefits of DGs, some technical issues need to be addressed. Islanding condition is one of the most important issue in this context. Until now, several islanding detection techniques have been proposed for detecting the islanding condition. This paper presents a brief overview of existing islanding detection techniques with their relative merits and demerits. Apart from …
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
Faculty of Engineering University of Malaya
Smart grid (SG) application is being used nowadays to meet the demand of increasing power consumption. SG application is considered as a perfect solution for combining renewable energy resources and electrical grid by means of creating a bidirectional communication channel between the two systems. In this paper, three SG applications applicable to renewable energy system, namely, distribution automation (DA), distributed energy system-storage (DER) and electrical vehicle (EV), are investigated in order to study their suitability in Long Term Evolution (LTE) network. To compensate the weakness in the existing scheduling algorithms, a novel bandwidth estimation and allocation technique and a new …
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
Faculty of Engineering University of Malaya
Smart grid (SG) application is being used nowadays to meet the demand of increasing power consumption. SG application is considered as a perfect solution for combining renewable energy resources and electrical grid by means of creating a bidirectional communication channel between the two systems. In this paper, three SG applications applicable to renewable energy system, namely, distribution automation (DA), distributed energy system-storage (DER) and electrical vehicle (EV), are investigated in order to study their suitability in Long Term Evolution (LTE) network. To compensate the weakness in the existing scheduling algorithms, a novel bandwidth estimation and allocation technique and a new …
H6-Type Transformerless Single-Phase Inverter For Grid-Tied Photovoltaic System
H6-Type Transformerless Single-Phase Inverter For Grid-Tied Photovoltaic System
Faculty of Engineering University of Malaya
There has been an increasing interest in transformerless inverter for grid-tied photovoltaic (PV) system because of the benefits of lower cost, smaller volume as well as higher efficiency compared with the ones with transformer. However, one of the technical challenges of the transformerless inverter is the safety issue of leakage current which needs to be addressed carefully. In addition, according to the international regulations, transformerless inverter should be capable of handling a certain amount of reactive power. In this study, a new H6-type transformerless inverter for grid-tied PV system is proposed that can eliminate the threat of leakage current. The …
Q-Switched Brillouin Fibre Laser With Multi-Wall Carbon Nanotube Saturable Absorber
Q-Switched Brillouin Fibre Laser With Multi-Wall Carbon Nanotube Saturable Absorber
Faculty of Engineering University of Malaya
A Q-switched Brillouin fibre laser (BFL) is successfully demonstrated using multi-walled carbon nanotubes (MWCNTs) embedded in polyvinyl alcohol (PVA) film as a passive saturable absorber (SA) for the first time. The SA is obtained by sandwiching the developed MWCNTs-PVA film between two FC/PC fibre connectors after depositing index-matching gel onto the fibre ends. The proposed Q-switched BFL incorporates a 5 km long dispersion shifted fibre in a ring cavity structure to generate Stokes shifted by 0.08 nm from the Brillouin pump wavelength. The BFL starts to generate a Q-switching pulse train at threshold pump power of 5 dBm. As the …
Rotation Invariant Bin Detection And Solid Waste Level Classification
Rotation Invariant Bin Detection And Solid Waste Level Classification
Faculty of Engineering University of Malaya
In this paper, a solid waste bin detection and waste level classification system that is rotation invariant is presented. First, possible locations and orientations of the bin are detected using Hough line detection. Then cross correlation is calculated to differentiate the true bin position and orientation from those of other similar objects. Next, features are extracted from the inside of the bin area and together with detected bin corners they are used to determine the bin's waste level. A few features are also obtained from the outside of the bin area to check whether there is rubbish littered outside the …
Optimal Multiple Distributed Generation Output Through Rank Evolutionary Particle Swarm Optimization
Optimal Multiple Distributed Generation Output Through Rank Evolutionary Particle Swarm Optimization
Faculty of Engineering University of Malaya
The total power losses in a distribution network are usually minimized through the adjustment of the output of a distributed generator (DG). In line with this objective, most researchers concentrate on the optimization technique in order to regulate the DG's output and compute its optimal size. In this article, a novel Rank Evolutionary Particle Swarm Optimization (REPSO) method is introduced. By hybridizing the Evolutionary Programming (EP) in Particle Swarm Optimization (PSO) algorithm, it will allow the entire particles to move toward the optimal value faster than usual and reach the convergence value. Moreover, the local best (P-best) and global best …
Recursive Construction Of Output-Context Fuzzy Systems For The Condition Monitoring Of Electrical Hotspots Based On Infrared Thermography
Faculty of Engineering University of Malaya
Infrared thermography technology is currently being used in various applications, including fault diagnosis in electrical equipment. Thermal abnormalities are diagnosed by identifying and classifying the hotspot conditions of electrical components. In this article, a new recursively constructed output-context fuzzy system is proposed to characterize the condition of electrical hotspots. An infrared camera is initially used to capture the thermal images of components with hotspots, and intensity features are extracted from each hotspot. The Recursively Constructed Fuzzy System (RCFS) is then applied to automatically realize and formulate the conditions of the thermal abnormalities. On the basis of the priority level, the …
Too Enthusiastic To Care For Safety: Present Status And Recent Developments Of Nanosafety In Asean Countries
Faculty of Engineering University of Malaya
Nanotechnology has the prospect to vibrate the imagination of human being and has the ability to be used in almost every sector of human need. With its limitless potentials, there are many environmental, health and safety related concerns due to extremely ambivalent effects of nanoparticles. Studies revealed that nanoparticles can enter the human body through the lungs, intestinal tract, and skin. Therefore, the researchers and workers who handle nanoparticles and nanomaterials can theoretically and primarily be affected, whereas on the consumers this will have secondary effects. This paper aims at sharing and evaluating the investment scenario, present status and recent …
Mode-Locked 2 Mu M Fiber Laser With A Multi-Walled Carbon Nanotube As A Saturable Absorber
Mode-Locked 2 Mu M Fiber Laser With A Multi-Walled Carbon Nanotube As A Saturable Absorber
Faculty of Engineering University of Malaya
We propose and demonstrate a passively mode-locked fiber laser operating at 1951.8 nm using a commercial thulium-doped fiber (TDF) laser, a homemade double-clad thulium-ytterbium co-doped fiber (TYDF) as the gain media, and a multi-walled carbon nanotube (MWCNT) based saturable absorber (SA). We prepare the MWCNT composite by mixing a homogeneous solution of MWCNTs with a diluted polyvinyl alcohol (PVA) polymer solution and then drying it at room temperature to form a film. The film is placed between two fiber connectors as a SA before it is integrated into a laser ring cavity. The cavity consists of a 2 m long …
Simulation Of Unsteady Heat And Mass Transport With Heatline And Massline In A Partially Heated Open Cavity
Faculty of Engineering University of Malaya
A computational work is performed to investigate the transient heat and mass transfer inside a ventilated enclosure. The enclosure has two ventilation ports as inlet and outlet. Three different configurations are tested according to location of outlet ports while location of inlet port is fixed. In case 1, the outlet port is located on the top of the left vertical wall, in case 2 at the right and case 3 at the middle of the ceiling. Finite element method is employed to solve the governing equations of flow, heat and mass transfer. Also, the heatline and massline techniques are used …
A Distributed Particle Filtering Approach For Multiple Acoustic Source Tracking Using An Acoustic Vector Sensor Network
Faculty of Engineering University of Malaya
Different centralized approaches such as least-squares (LS) and particle filtering (PF) algorithms have been developed to localize an acoustic source by using a distributed acoustic vector sensor (AVS) array. However, such algorithms are either not applicable for multiple sources or rely heavily on sensor-processor communication. In this paper, a distributed unscented PF (DUPF) approach is proposed for multiple acoustic source tracking. At each distributed AVS node, the first-order and the second-order statistics of the local state are estimated by using an unscented information filter (UIF) based PF. The UIF is employed to approximate the optimum importance function due to its …
A Comparative Study Of Multi-Objective Optimal Power Flow Based On Particle Swarm, Evolutionary Programming, And Genetic Algorithm
Faculty of Engineering University of Malaya
This paper compares the performance of three population-based algorithms including particle swarm optimization (PSO), evolutionary programming (EP), and genetic algorithm (GA) to solve the multi-objective optimal power flow (OPF) problem. The unattractive characteristics of the cost-based OPF including loss, voltage profile, and emission justifies the necessity of multi-objective OPF study. This study presents the programming results of the nine essential single-objective and multi-objective functions of OPF problem. The considered objective functions include cost, active power loss, voltage stability index, and emission. The multi-objective optimizations include cost and active power loss, cost and voltage stability index, active power loss and voltage …
Multilevel Voltage Source Inverter With Optimised Usage Of Bidirectional Switches
Multilevel Voltage Source Inverter With Optimised Usage Of Bidirectional Switches
Faculty of Engineering University of Malaya
This study presents a multilevel voltage source inverter that has been designed to reduce circuit complexity by optimising the use of bidirectional switches. The proposed inverter is built by adding an auxiliary circuit comprising an arrangement of bidirectional switches to the three-phase, six-switch, full-bridge configuration. Several bidirectional switches are made to function in the optimised mode in which their operations are divided among the three phases. The presence of the optimised mode considerably reduces the number of power switches as the number of levels in the line-to-line voltage waveform increases. A novel modulation scheme based on space vector concept with …
A Q-Switched Fibre Laser Operating In The 2 Mu M Region Based On Nonlinear Polarization Rotation Technique
Faculty of Engineering University of Malaya
We demonstrate a Q-switched fibre laser operating at 1949.0 nm, which is based on a nonlinear polarization rotation (NPR) technique. It uses a 2 m long commercial thulium-doped fibre and a 15 m long homemade thulium-ytterbium co-doped fibre as active media. They are pumped respectively by 800 nm single-mode and 905 nm multimode radiations. A stable Q-switched pulse train with the repetition rate 13.49 kHz and the pulse width 3.089 mu s is obtained when the 905 nm and 800 nm pump powers are fixed at 2.3 W and 110.4 mW, respectively. The maximum pulse energy, 11 nJ, is obtained …
Study On Coarsening Of Ag3sn Intermetallic Compound In The Fe-Modified Sn-1ag-0.5cu Solder Alloys
Study On Coarsening Of Ag3sn Intermetallic Compound In The Fe-Modified Sn-1ag-0.5cu Solder Alloys
Faculty of Engineering University of Malaya
The present study focuses on coarsening of Ag3Sn intermetallic compound in the Sn-1Ag-0.5Cu and Fe-modified Sn-1Ag-0.5Cu solder alloy. The investigations showed that the Ag3Sn intermetallics coarsened rapidly in the Sn-1Ag-0.5Cu solder alloy whereas the Ag3Sn intermetallics were found to be quite stable in the Fe-modified Sn-1Ag-0.5Cu solder alloy. The lattice strain in the Ag3Sn intermetallics and the blocking effect on Ag diffusivity in Sn matrix suggested the possible mechanisms for the coarsening suppression of the Ag3Sn intermetallics in the Fe-modified solder alloy. (C) 2014 Elsevier B.V. All rights reserved. Link to Full-Text Articles : http://www.sciencedirect.com/science/article/pii/S0925838814024621
Zigbee-Based Data Acquisition System For Online Monitoring Of Grid-Connected Photovoltaic System
Zigbee-Based Data Acquisition System For Online Monitoring Of Grid-Connected Photovoltaic System
Faculty of Engineering University of Malaya
For grid-connected photovoltaic (PV) system, monitoring is considered as a crucial aspect for observing the stability and performance of the system. The simplest method is to have the data collected and transmitted across data cables. Due to the cost and technical limitations of the data cable, the monitoring station needs to be located reasonably close to the monitored plant. Apart being inconvenient, the use of data cable often adds capital and maintenance cost to the system. In this research project, a Zigbee-based wireless monitoring system is developed for online monitoring of a grid-connected photovoltaic system. Parameters like temperature, irradiation, PV …
Development Of Novel Passive Check Valves For The Microfluidic Cd Platform
Development Of Novel Passive Check Valves For The Microfluidic Cd Platform
Faculty of Engineering University of Malaya
Microfluidic CD platforms are utilized to perform different biological processes and chemical analyses. In general, a microfluidic CD implements the centrifugal force that is created by the spinning of the platform to pump liquid through the microfluidic network of chambers and channels. Over the last few decades, a wide range of active and passive valving methods were proposed and tested on various microfluidic platforms. Most of the presented valves are too complex to design and involve lengthy fabrication processes. In this paper, easy to fabricate air and liquid check valves for centrifugal microfluidic platforms are presented: a Terminal Check Valve …
Development Of Nanoengineered Thulium-Doped Fiber Laser With Low Threshold Pump Power And Tunable Operating Wavelength
Faculty of Engineering University of Malaya
A tunable and low-threshold thulium (Tm)-doped fiber (TDF) laser is demonstrated using a new silica-based nanoengineered TDF in a linear configuration, in conjunction with 1552-nm pumping. The TDF used in these experiments had a Tm-doped nanoengineering yttrium-alumina-silica glass core with a diameter of 13.43 mu m and 0. 21 NA, which is surrounded by a pure silica inner cladding with normal acrylate polymer resin coating. The nanoengineered TDF was fabricated using a modified chemical vapor deposition (MCVD) process, in conjunction with a solution-doping technique. The fabricated fiber shows an absorption loss of 165 dB/m at 793 nm. A maximum lasing …
A Configurable Architecture For Fast Moments Computation
A Configurable Architecture For Fast Moments Computation
Faculty of Engineering University of Malaya
No abstract provided.
Enhancement Of Thulium-Ytterbium Doped Fiber Laser Efficiency Using Dual-Pumping Method
Enhancement Of Thulium-Ytterbium Doped Fiber Laser Efficiency Using Dual-Pumping Method
Faculty of Engineering University of Malaya
Performance enhancement of laser acquired from a newly developed double-clad Yb3+/Tm3+ codoped fiber (YTDF) is demonstrated using dual-pumping scheme. The laser uses a 2 m long YTDF fiber with a core dopant concentrations (in wt%) of 2.00 Yb2O3, 0.5 Tm2O3, 1.0 Al2O3, and 3.00 Y2O3 as a gain medium in conjunction with a pair of fiber Bragg grating in a linear cavity resonator to generate lasing at 1901.6 nm. The best efficiency of 2.9% and the highest output power of 27 mW are obtained by combining 927 nm pump with 905 nm pump. As compared to a single pumping scheme …
Effective Utilization Of Excess Energy In Standalone Hybrid Renewable Energy Systems For Improving Comfort Ability And Reducing Cost Of Energy: A Review And Analysis
Faculty of Engineering University of Malaya
One of the features that characterize renewable energy sources is their variability and intermittency. Intermittency covers both the predictable and unpredictable variations of their power outputs and uncertainty in the power availability. To overcome the drawback of intermittency, special design considerations should be taken into account. These additional design considerations increases the overall cost of the renewable energy systems. Adding storage system and/or backup source to the renewable sources is one of the measures used to guarantee the continuity of power supply to the loads, and therefore improve the reliability of the renewable energy systems. The operation of renewable energy …
Fabrication And Characterization Of Microstacked Pzt Actuator For Mems Applications
Fabrication And Characterization Of Microstacked Pzt Actuator For Mems Applications
Faculty of Engineering University of Malaya
A microstacked PZT actuator of dimensions 8 mmx 0.8 mm x 0.4 mm and capable of 2.3-mu m actuation under a voltage of 100 V was fabricated and characterized. This actuator was then integrated into a silicon microstage with dimensions of 20 mm x 20 mm x 0.4 mm requiring actuation by a miniaturized actuator. The microstage was designed containing a Moonie amplification mechanism in order to further amplify the actuation of the stacked PZT actuator. Experimental characterization of the microstage performance indicated that the combination of a stacked PZT actuator with the Moonie amplification mechanism was successful in enabling …
Experimental Validation Of Minimum Cost Function-Based Model Predictive Converter Control With Efficient Reference Tracking
Faculty of Engineering University of Malaya
This study proposes a robust and powerful finite control set-model predictive control (MPC) algorithm to control the load current with lower total harmonic distortion and efficient reference tracking. In this control, the cost functions are determined for all the possible switching states of the converter and a switching state is selected corresponding to the minimum cost function for actuating the converter in the next sampling time period. To justify the performance of the proposed MPC scheme, a comprehensive study with the carrier-based pulse-width modulation, hysteresis current control and proposed minimum cost function-based MPC of the three-phase load current has been …
Fuzzy Swinging-Up With Sliding Mode Control For Third Order Cart-Inverted Pendulum System
Fuzzy Swinging-Up With Sliding Mode Control For Third Order Cart-Inverted Pendulum System
Faculty of Engineering University of Malaya
Cart Inverted Pendulum (CIP) system is a benchmark problem in nonlinear automatic control. In this paper, two third-order differential equations were derived to create a combining model for the cart-pendulum with its DC motor dynamics. Motor voltage was considered the system input in the presented model. The friction between the cart and rail was included in the system equations through a nonlinear friction model. Fuzzy Swinging-up controller was designed to swing the pendulum to the upright position, once reaching the upward position; Sliding Mode Controller (SMC) is activated, to balance the system. In order to verify the performance of the …
Optical Fiber Based Dosimeter Sensor: Beyond Tld-100 Limits
Optical Fiber Based Dosimeter Sensor: Beyond Tld-100 Limits
Faculty of Engineering University of Malaya
This work investigates the suitability of single mode optical fibers (SMFs) as ionizing radiation dosimeter sensors. Thermoluminescence (TL) response studies have been carried out to investigate the performance of two commercial optical fibers, SMF-1 and SMF-2, with different Ge-doping concentrations of 4.9 and 4.3 wt%, respectively, exposed to 0.5 to 8 Gy doses under 6, 9, and 20 MeV electron radiations. The performance parameters include dose response linearity and sensitivity, energy dependency, glow curve analysis, minimum detectable dose, repeatability, fading effects and optical absorption. The TL dose response of SMF-1, the fiber with the greater Ge concentration of the two, …
A Selector-Combiner Circuit For Multi-Pixel Cmos Photon Detector
A Selector-Combiner Circuit For Multi-Pixel Cmos Photon Detector
Faculty of Engineering University of Malaya
This paper presents a selector-combiner (SC) circuit for use as a constituent block for a multi-pixel complementary metal-oxide-semiconductor (CMOS) photon detector. The circuit essentially allows signal from pixels of interest to be summed and output. This pixel-selection configurability may enhance imaging performance and also produce different imaging effects for various analyses. A 9-to-1 SC circuit was designed and fabricated in an Austriamicrosystems (AMS) 0.35 mu m process technology. The worst-case linear working range at the input was found to be between 1.50 and 1.80V, occurring when all inputs were enabled. It exhibited an insignificant signal loss of about -0.96dB when …